Most vehicles traveling over naturally occurring terrain use some sort of flexible medium to actually contact the ground. This is essential in order to accommodate the various obstacles and irregularities of the earth's surface, as well as to provide some degree of shock absorption to the rest of the vehicle. Unfortunately, the flexible medium, usually a rubber like material, does not offer sufficient traction with many types of surfaces. In order to improve the grip of the track or tire with particularly slippery or smooth surfaces, pointed projections, commonly referred to as studs, are mounted in some fashion on the flexible ground engaging material.
An early example of such a stud is shown in U.S. Pat. No. 2,426,974, issued to Ragon. Ragon utilizes a fixed length projection or "calk" which is mounted to the surface of an interior layer of a tire, permitting the calk to project through the outermost layer of the tire and engage the ground.
An early snowmobile stud is shown in U.S. Pat. No. 3,572,851, issued to Schuler, discloses a laterally mounted cleat to which fixed length studs are rigidly mounted. The studs are formed as four sided projections with an open interior region through which the mounting hardware passes.
In an effort to provide an integrally formed track stud, U.S. Pat. No. 3,767,275, issued to Russ, discloses an imbedded member which resides in a raised area of the track. Once the individual fixed length studs wear or become damaged in use, the entire track must be replaced.
The traction device state of the art has evolved toward individual traction elements placed on the snowmobile track by the end user. Studs of this type are shown in U.S. Pat. No. 3,782,787, issued to Rubel et al, which utilizes pairs of fixed length studs mounted oil a common, track engaging base.
An individual after market stud is shown in U.S. Pat. No. 3,785,420, issued to Bradley et al. The ground engaging element is a pronged cleat that abuts the outer surface of the track and projects a fixed distance therefrom. Similar types of ice engaging cleats are shown in U.S. Pat. Nos. 3,930,689, 3,973,808, 4,049,315 and 3,865,441.
Single, discrete pointed and blunt nosed fixed length studs proliferate in the endless track state of the art. Examples of such studs are shown in U.S. Pat. Nos. 3,838,894 and 5,234,266. The effectiveness of these studs is hampered by the fact that they are mounted in the flexible, nonreinforced region of the track. When the stud is forced into the ice or earth due to the weight of the snowmobile, the resilient track is free to recoil or deflect upwardly in the region of the stud, thus reducing the degree of ice penetration achieved by the stud.
While all of the aforementioned studs are both fixed length and rigid, some attempts have been made to address the problem of stud length which, ideally, must vary according to the specific type of terrain encountered, the amount of stud wear which has already occurred and the vehicle speed and weight. One proposed solution has been to make a stud of a flexible material as shown in U.S. Pat. No. 4,095,849, issued to Husted. Another proposed solution has been to affix the stud to a resilient or deformable mount, as shown in U.S. Pat. No. 4,218,101.
However, none of the studs and stud mounting arrangements previously devised has addresses the underlying problem of having a fixed length stud which has a length which may be readily adjusted by the end user on a daily basis. The traction advantages of a fixed length stud are many, but heretofore alteration in the length of such a stud could only be accomplished by replacing the stud itself, which is a time consuming process.